Development of Analytical Method for Levofloxacin, Clarithromycin and Azithromycin in Influent and Secondary Effluent and Their Adverse Effects on Algal Growth

The pollution of water resources by pharmaceuticals is an emerging public concern in many developed countries. The purpose of this study was to establish an analysis method of antibiotics in secondary effluent and to evaluate its detected concentration from the viewpoint of biological effect. We developed a novel analysis method for levofloxacin (LVFX), clarithromycin (CAM) and azithromycin (AZM) in wastewater using LC/MS/MS, with detection limits of 0.24–4.9 ng/l and recovery ratio of 93–108 %. The concentrations of LVFX, CAM and AZM in the influent of six wastewater treatment plants (WWTPs) that used the activated sludge process were 552, 647 and 260 ng/l, respectively, and in the secondary effluent, 301, 359 and 138 ng/l, respectively. We also evaluated the concentrations of LVFX and CAM in secondary effluents using an algal growth inhibition test. The concentrations of LVFX and CAM in secondary effluents were below their respective no-effect concentrations (NECs). On the other hand, the predicted environmental concentration suggests that the NEC ratio (PEC/PNEC) of CAM would exceed fourteen at the maximum in the secondary effluent if a safety factor of one hundred were set. This suggests a risk of algal growth inhibition due to CAM in WWTP discharge if it is insufficiently diluted in the receiving waters.